While hydrogen (H2) has been proposed for use as an alternative fuel for internal combustion engines, hydrogen's physical properties make it difficult to handle. Hydrogen's low energy density and atomic weight makes storage and transport expensive.
Anhydrous ammonia (NH3), on the other hand, stores and handles very much like liquefied petroleum gas (LPG). For example, ammonia has a boiling temperature of about −33.5° C. at 1.013 bar (1 atmosphere). Similarly, propane, the main constituent of (LPG) has a boiling temperature of about −42.1° C. Furthermore, ammonia is carbon free and renewable in addition to being reasonably practical to handle, store and transport.
Also, from an energy density standpoint, ammonia is much better than even liquefied hydrogen. On a volume bases, the energy density of liquefied hydrogen is about 8,491 kJ/liter compared to liquefied ammonia having an energy density of about 11,308 kJ/liter.
As indicated by its chemical formula, NH3, ammonia is one (1) part nitrogen and three (3) parts hydrogen. By atomic weight, ammonia is fourteen (14) parts nitrogen to three (3) parts hydrogen, or approximately 82% nitrogen to 18% hydrogen. However, while ammonia is only 18% hydrogen, the fact that there are 3 hydrogen atoms attached to a single nitrogen atom allows ammonia to contain significantly more hydrogen by volume than even liquefied hydrogen.
However, one problem with ammonia is flame propagation. Ammonia has a minimum ignition energy of about 680 mJ. By contrast, hydrogen has a minimum ignition energy of about 0.011-0.017 mJ and gasoline has a minimum ignition energy of 0.8 mJ. Consequently, the flame propagation speed of ammonia/air mixture is slow and it is difficult to realize high cycle efficiency because of the long combustion duration.
To maximize the benefit of ammonia as a fuel for internal combustion engines, a fuel injector, a fuel system and method of providing fuel to an internal combustion engine are disclosed that includes producing a certain percentage of hydrogen from ammonia itself to accelerate ammonia combustion.